The apparatus of the present invention relates to an incubator for a biological indicator used to monitor the effectiveness of a sterilization process. More particularly, the invention is directed to an optical viewing system or arrangement for an incubator which facilitates viewing of a sterilization indicator which includes a receptacle.
Such an incubator may be any of a variety of shapes and sizes, but preferably is configured to accept a plurality of such receptacles, for simultaneously incubating the contents of the sterilization indicators. Heretofore, it has been the practice to provide a transparent or translucent portion of the receptacle, so that the contents thereof may be viewed by removing the receptacle from the incubator. However, individual handling and identification of receptacles could be simplified by providing means for viewing the contents of the receptacle while still in the incubator. In this regard, the present invention is directed to a novel optical arrangement or system to enable viewing of the contents of each receptacle while the receptacle remains in the incubator apparatus.
At this point, a brief general description of the structure and use of such a sterilization indicator may prove helpful in understanding the invention.
In order to test the effectiveness of a steam or gas sterilization process, standardized spores of a bacterial strain sufficiently resistant to the sterilization medium are placed on a carrier, such as a spore disc or strip, and the strip is exposed to the sterilization medium being tested, normally gas, steam or dry heat. Destruction of the standardized spore strain insures sterilization of the bacterial strain in the chamber of the autoclave or other sterilization device. On the other hand, the presence or survival of these standardized spore strains indicates an unsatisfactory sterilization process.
After the sterilization process has been completed, the survival of the spores is determined by mixing a test solution containing a culture or growth medium and a pH indicator with the bacterial spores and thereafter incubating the culture for growth. In spore fermentation, for example, glucose contained in the growth medium is utilized by viable or living spores, and pyruvic acid is produced as a byproduct. The pyruvic acid lowers the pH of the test solution and results in a change of color of the pH indicator in the solution. If there are no living or viable spores following sterilization, the pH and the color of the test solution remains essentially unchanged. Hence, the pH indicator in the solution acts as an indication of the effectiveness of the sterilization process.
Various ways are known for mixing the test solution with the strips containing the microorganisms or spores. One such way consists of providing a hermetically sealed glass ampule containing the culture medium and enclosing the ampule and the test strip in a container or receptacle and providing a means to crush the ampule whereby the culture medium floods the test strip in the receptacle. Thereafter, the saturated test strip in the receptacle is incubated for the requisite period of time in order to determine whether or not viable bacteria is present. The receptacle has a transparent or translucent portion to permit viewing of the color of the test solution and pH indicator. Devices of the foregoing type are shown, for example, in U.S. Pat. Nos. 3,440,144; 3,661,717 and 4,304,869.
As previously indicated, the present invention is an improvement on incubator devices or apparatus used in the foregoing procedure. In this regard, it is also desirable to provide an incubator apparatus for handling a plurality of receptacles which is relatively compact and simple to operate. Additionally, it is desirable to provide for simultaneous viewing of the color of the test solution in each of a plurality of receptacles within the incubator. Advantageously, the optical structure or arrangement of the present invention makes possible such simultaneous viewing while maintaining compactness, by arranging a plurality of receiving wells for the receptacles in an array of rows and columns. A convenient viewing window is provided adjacent an entrance aperture or opening to each of these receiving wells. The novel optical system of the invention passes light from a suitable source through a translucent portion of each of the receptacles for viewing the color of the test solution therein at the associated viewing window.